Membrane components of normal and pathologic erythrocytes will be investigated to identify structural and energetic factors which contribute to the maintenance of red cell shape and deformability. Spectrin appears to be membrane polypeptides critical for maintaining normal shape and deformability. Studies on the chemical events occurring during phosphorylation of spectrin by protein kinase will be extended. The sequence of amino acids around the site(s) of phosphorylation will be determined. The mechanism associated with spectrin dephosphorylation during and concommitant determinations on cell morphology and deformability during metabolic depletion of the red cell will be studied in some detail. Membrane polypeptides from pathologic erythrocytes such as hereditary spherocytes, elliptocytes, and pyropoikilocytes will be examined by a variety of electrophoretic and immunologic techniques to try to identify dysfunctional components. The interaction of spectin with erythrocyte actin will be studied in preparations from normal and pathologic cells. Additional studies on the thermal sensitivities of normal and pathologic erythrocytes will be used to probe constituents in defective membranes. The properties of red cells in a murine genetic disorder (sph/sph) involving a spectrin deficiency will be studied further to evaluate the role of spectrin in maintaining a stable membrane and influencing fluidity properties of the membrane.